PROJECT SUMMARY/ABSTRACT. Human aging is accompanied by a range of progressive chronic diseases with inflammatory etiology (e.g., atherosclerosis and TNF-?-driven pathologies such as rheumatoid arthritis), as well as by elevated acute inflammatory responses, such as upon infection by influenza virus. These conditions remain in clear need of new therapeutic interventions. Recent evidence from our labs and other groups has revealed that an as-yet unexploited kinase, RIPK3, drives disease progression in settings of both chronic and acute inflammation, including in each of the examples mentioned above. RIPK3 is the central mediator of a highly pro-inflammatory form of cell death termed `necroptosis', or programmed necrosis. In atherosclerosis and TNF-?-mediated pathologies (such as rheumatoid arthritis, and ulcerative colitis), RIPK3-initiated necroptosis mediates release of danger-associated molecular patterns that amplify inflammation and drive disease progression. During acute influenza A virus (IAV) infection, RIPK3-mediated necroptosis underlies necrotic lung damage, which is an established instigator of two major morbidities in the elderly ? viral pneumonia and acute respiratory distress syndrome (ARDS). Thus, RIPK3 is a very attractive new molecular target for multiple age-related pathologies. Curiously, given how important a therapeutic target RIPK3 potentially is, no selective RIPK3 inhibitors are in clinical use or ever been advanced into clinical trials. We now have developed a new structural class of RIPK3 inhibitors, which we call the UH15 series, and which are based on a pyrido[2,3-d]pyrimidine scaffold that targets both the ATP- as well as the allosteric Glu-out pockets of the kinase. Our preliminary findings reveal that UH15 analogs, after just one round of optimization, are already more potent than current RIPK3 blockers. These exciting results highlight the immediate translational potential of the UH15 series for a variety of chronic and acute inflammatory diseases of high relevance to the elderly. As no chemical probes exist to validate this novel biological target, RIPK3, in vivo, the immediate goals of our proposal are to iteratively optimize UH15 based compounds for RIPK3 blockade in vivo (Aim 1) and to use these chemical probes to directly assess the therapeutic efficacy of targeting RIPK3 kinase in vivo in mouse models of age-related chronic and acute inflammatory conditions, including atherosclerosis and TNF-driven pathology (Aim 2), and influenza virus- triggered morbidities (Aim 3). The proposed studies bring together three labs with strong, complementary expertise in RIPK3 kinase chemistry and function during inflammation (Degterev), RIPK3-mediated cell death signaling and IAV pathogenesis (Balachandran), and small-molecule medicinal chemistry (Cuny). Successful completion of these Aims has the potential to transform our treatment of multiple age-related inflammatory conditions.